It is very easy to use Ortelius to create documentation of your actionscript classes.

To create the doumentation you need to go through 3 steps.
1. Choose the class-files you want to documentate
2. Choose the folder where you want the documentation to be
3. Click to generate the documentation

Better documentation with javadoc tags
If you just do a descibed abowe, you will get a good overview of the methods and properties of your classes, but it wont be very descriptive.

To improve your documentation you need to add the javaDoc comments to your classes, that explain what your method are doing etc.

Good practise
It is good practise to add your javadoc tags and description while you are coding the class, and dont wait for a better time do it - because chances is that you wont find time to do it latter. Or even better; do it while you are designing the architecture of your application. My favorite application for this purpose is StarUML, that can export Actionscript stub files with javadoc tags based on the description you have made in StarUML.
>> Get StarUML
>> Get an Actionscript template that supports javadoc